Humans have various medical conditions that alter their ability to see. The so-called standard viewer is able to differentiate between multiple colors, resolve specific shapes at a standard distance, and see under specific lighting conditions. The so-called standard viewer also has the ability to maintain psychological stability despite ambient darkness. The deviation of the physiological and mental state from that of the standard viewer is considered a medical condition when the deviation obstructs daily living.
APPLICATION FOR PRESBYOPIA: As people age, they commonly lose the ability to focus on both near and far objects. This phenomenon is commonly called senior vision or presbyopia in medical language. Presbyopia happens because of the natural hardening of the lens in a viewer's eye. The hardening results in a decreased ability for the muscles to contract and expand the shape of the lens. The loss of near vision causes the most obstacles for daily life and viewers augment their vision with a low power magnification in the form of reading glasses. However, the natural progression of presbyopia is not limited to near vision, but also far vision because of the progressive hardening of the lens as described above.
FIG. 2 shows the natural physiological mechanism of focusing on an object. The eye perceives the letter ‘E’ (201) at some distance. To focus the object into the viewer's central vision (206), the eye muscles (203) modulate the shape of lens (204) so that the lens will focus the object ‘E’ onto the retina (206). The hardening of the lens causes the eye muscles to be insufficient in changing the lens form and the object cannot focus onto the retina. FIG. 3 shows the object ‘E’ (301-304) in focus as perceived by a young viewer, while FIG. 4 shows the object ‘E’ (401-404) by a view with presbyopia that is unable to focus the object onto the retina.
Viewers with presbyopia can still see clearly, but their visual focus is limited to a narrow range of distances. For the purposes of this patent, it is useful to know that such viewers can see objects clearly at a distance of 1-2 m.
Common optics can correct for this visual deficit, however conventional optics can only correct for a single focal point. For example, reading glasses often seen in drug stores an enable a viewer with presbyopia to see clearly near objects, but the same lens cannot be used for objects far away. FIG. 5 shows the usage of concave lens (501) to correct for myopia (inability to focus on far objects) and FIG. 6 shows the usage of convex lens (601) to correct for the near distances in presbyopia.
More sophisticated optics were introduced by the bifocal lens, whereby the upper half of the lens is constructed to assist viewers for far distance view (702), while the lower half of the lens is constructed to assist viewers for near distance view (703). This enables a user with presbyopia to view both near and far with a single pair of glasses. FIG. 7 shows an example of progressive lens (701) simultaneously correcting for near (703) and far (702) distances, albeit near and far distance focus is restricted to lower and upper visual fields, respectively.
However, conventional bifocal lens enables a viewer to focus on near and far by separating the lens areas. For example the lower portions of the lens cannot be used to perceive objects at a far or even normal distance. One example of this challenge is for a viewer wearing bifocal lens to descend a flight of stairs. The bifocal lens enables a view to read objects 30-45 cm, but in turn, obstructs the view from perceiving objects at a distance of 1-2 m, including the view's own feet and the next step in the stair case. This causes significant concern for views trying to descend a flight of stairs.
Another commonly mentioned challenge is a viewer with presbyopia trying to enjoy a round of golf. Bifocal lens enables a user to read a scorecard, but prohibits the viewer from focusing on a golf ball (801) when taking a shot as in FIG. 8. After taking a shot, the viewer can only see the ball in flight with the upper half of the visual field because the lower half can only focus on near objects.
Such societal needs call for a pair of glasses that is comfortable to wear, enables a wide field of view, and enables a viewer to simultaneously see objects at near and far distances in focus without restriction on upper and lower visual fields as seen in bifocal glasses.
APPLICATION FOR COLOR BLINDNESS: The eye perceives light through photoreceptor cells called Rods and Cones located in the retina of the eye (FIG. 11). Light energy elicits a cellular reaction whereby the ionic composition internal to the photoreceptor cells triggers a nerve impulse which is transmitted to the brain as a light signal. Rods (1102 and 1104) and Cones (1103) are found on an array and the selective triggering of these photoreceptors translates light images into a visual image perceived by the brain.
Color is perceived by Cones. There are three types of Cones, each with photoreceptors that enables selectivity for the three primary colors, red, green, and blue. Each red, green, and blue Cone photoreceptor has protein structures that react to light energy with wavelengths correlating to red, green, and blue light. The gene that codes for these protein structures is X-linked (found on the non-redundant arm of the X-Chromosome), and therefore males have a propensity to have genetic deficits associated with Cone photoreceptors. The sensitivity of these Cone photoreceptors is shown in FIG. 12. The first type of Cone has the sensitivity shown as the curve marked (1201) or L (long wavelength), the second type of Cone has the sensitivity of the curve marked (1202) or M (middle wavelength) and the third type of Cone has the sensitivity of the curve marked (1203) or S (short wavelength). The horizontal axis is wavelength and the vertical axis is the normalized sensitivity to each peak.
The impact of having a genetic deficit on the cone photoreceptor is the inability to differentiate that specific color. A genetic mutation located on the second type of Cone photoreceptor (whose sensitivity is the curve marked M or 1202 and hereafter called as Green Cone) will be used as it is the most prevalent. Green light may enter the eye and strike the photoreceptor layer of the retina, however, no or little of Green Cone photoreceptor reacts to the light because of the genetic deficit. Green light fails to trigger a nerve response and therefore the brain does not perceive this wavelength of light. The brain is still able to perceive red and blue light and therefore, this patient will see the world in two colors, red and blue. This is the mechanism of color blindness.
FIG. 13 shoes the population of normal vision and color blindness. The weak sensitivity of the first type of Cone photoreceptor (Red) is called as protanomaly and weaker sensitivity is called as protaopia. Similar way, the second type of Cone photoreceptor (Green) deficit is deuteranomaly and deuteraopia respectively. The third type of Cone photoreceptor (Blue) deficit is called as Tritanomaly and Tritaopia respectively. The second type Cone deficit has the largest population among color blindness and 2.7% (deuteranomaly) and 0.56% (deuteranopia). Complete color blindness (Achromatopsia) is very rare and less than 0.0001% as shown in FIG. 13. The color bars in FIG. 13 shows how each type perceive the color of spectrum.
FIG. 14 shows the patterns used for color blindness test. Normal vision sees the patterns (1401) which has red character of “6” over the background of yellow, green and blue and the pattern (1405) having green character of “74” over red and yellow background. Protanopic and Deuteranopic vison cannot discriminate red and green, therefore cannot see these characters as shown in (1402, 1403, 1406 and 1407), although Tritanopic vision can read these as shown in (1404 and 1408). FIG. 15 shows another example to show how images are perceived by each type of color blindness. The image (1501) is by Normal Vision. The image (1504) is by Protanopic Vision which loses red and a large part of green, because the sensitivity of the first type of Cone photoreceptor is overlapping from red to green. The image (1508) is by Deuteranopic Vision which loses green and a large part of red. The image (1510) is by Tritanopic Vision which loses blue.
It is important to note the mechanism of color blindness. A genetic deficit results in a change in photoreceptor protein shape, and in the majority of patients, this weakens the photochemical reaction. In other words, if the incoming light for the color in question is strengthened, a photochemical reaction can occur triggering a nerve response and the brain can perceive the color. In the above mentioned example of a green color blind patient, if a three color image were presented where the green color has significantly increased intensity, then this patient can differentiate between the three colors and perceive the world in red, green, and blue.
Such societal needs call for an apparatus that can capture the images of a patient's visual field, modulate the image by increasing the intensity of a specific color, and displaying this modified image to the patient. If images can be captured, modified, and displayed to the patient in real time, the patient can effectively enjoy daily life in three colors rather than two.
It is noteworthy to mention that such an apparatus can help patients with genetic deficits that weaken the photoreceptor reaction to a specific wavelength of light. If the genetic deficit rendered the photochemical receptor completely unreactive to the assigned wavelength, increasing the intensity will not enable correction of deficit. Fortunately, the majority of patients with color blindness have a weakness in perceiving green, and the apparatus of this invention will benefit the vast majority of color blind patients as shown in FIG. 13
APPLICATION FOR POOR NIGHT VISION: Over time, humans progressively lose night vision, or the ability to distinguish objects in darkness. The cause of this visual deficit can be multi-faceted with underlying conditions including, but not exclusive to, early cataracts, vitamin A deficiency, retinitis pigmentosa, and diabetes. Any progressive visual deficit warrants medical attention; however, not all conditions have immediately reversible treatments.
Such societal needs call for an apparatus that can capture the images of a patient's visual field in darkness, modulate the image to increase the brightness or render the image in such a way that objects can be distinguished, and display this modified image to the viewer. If such visual fields can be captured by image data, modified, and projected in real time, people can greatly enhance their ability to see in darkness.
SAFETY FEATURE FOR ALL APPLICATIONS: A safety factor that should not be missed is the importance of peripheral vision. Many people focus on the central vision or macular vision where the vision is perceived in color and the resolution is the highest. In contrast, peripheral vision has very low visual acuity and generally perceives in black and white. However, the brain receives many cues from the peripheral field which ultimately contribute to special awareness, motion detection, and depth perception. One good example is to wear a pair of goggles that restricts vision in the periphery; such views will find many activities of daily living become restricted. Therefore, it is desirable for corrective glasses to correct a wide field of view, however, ultimately leave a peripheral margin unobstructed to enable the viewer with nascent visual cues from the periphery.
Human eyes can see an image in high resolution and in color only in the central area of field of view as shown in (1605) of FIG. 16, but eyes can see very wide angle view in lower resolution and without color as wide as 180 degrees horizontally (from 1607 to 1604) and 120 degrees vertically (1606 to 1608) in FIG. 16.
In past years, preservation of the peripheral field for wearable displays was less of a concern. This is because wearable displays were either (1) completely opaque, or (2) covered only a minor aspect of the visual field. Eye-Trek by Olympus as shown in FIG. 21, and HMZ-T2 by Sony as shown in FIG. 22, are all wearable displays that are completely opaque. The peripheral vision is completely cut off by light shields and the visual field is meant to be as dark as possible except for the projected image. The designers of these products intentionally created their products in such a way to decrease the entrance of ambient light, which in turn increased the contrast ratio of the display, thus creating a better visual experience. Such products were not meant for wear during activities of daily living, but meant as personal theaters for viewers who wanted to concentrate on viewing the display. Such products do not need this safety feature because users will likely be seated and not moving about nor conducting over operations simultaneously.
On the other hand, Glass by Google as shown in FIG. 24, and MEG 4.0 by Olympus are both examples of wearable displays that cover a minor area of the visual field. The displays are meant to be worn while conducting activities of daily living, however, the majority of the visual field is unobstructed and therefore the users will have no issues in perceiving peripheral cues while using these products.
However, as wearable displays advance, it is expected that wearable displays will cover a ‘full field of view,’ and designed for simultaneous wear with activities of daily living. This invention seeks to be such a product whereby people with visual deficits such as presbyopia, color blindness, or poor night vision can enjoy life with a visual field that is corrected for the deficit. We expect this type of product to become useful when the display can project more than 13 degrees field of view from center and have a transparency exceeding 60%. The rationale for the field of view (13 degrees from center) is that it covers central vision (macular vision). Projection beyond that range enters into peripheral vision. 60% transparency refers to 60% of light is able to pass through the image-capture and display apparatus lens and enter into the user's eye. For a visual apparatus to be useful in daily living, the user must be able to see through the apparatus and see the visual field naturally, and we believe 60% transparency is the threshold whereby any less light would be considered obstructive for natural activities. For example, sunglasses diminish light transparency (transparency is under 60%), and although it is possible to conduct activities of daily living while wearing sun glasses, it is not considered natural. Another example is a standard pair of glasses for myopia (near sightedness). The field of view clearly exceeds 13 degrees from center and the transparency exceeds 60%. With myopia glasses, the user considers the visual field to be natural and wears them while simultaneously conducting activities of daily living.
When a user views through an image capture-display apparatus that can project more than 13 degrees from center with transparency exceeding 60%, we believe the user will require less cognitive thought. For example, when looking through ‘personal theater’ goggles such as Sony's HMZ-T1, the viewer clearly understands that the field of view is not natural and takes appropriate measures to prevent disorientation such as sitting down to view the image. However, if the image-capture display device is sufficiently transparent (more than 60%) and has a field of view that covers the entire central field and extends into the peripheral field (exceeds 13 degrees from center), the viewer will consider the visual field to be natural much the same way one considers the visual field when wearing myopia glasses.
When peripheral view is completely lost, the viewer loses visual cues such as motion and direction which becomes disorienting. This disorientation can result in falls or accidents while conducting activities of daily living. Ideally, an image-capture and display apparatus will capture the entire visual field and enable a user with a full field of peripheral vision. However, we believe that there is utility to maintaining a margin in the peripheral visual field that is unobstructed by the projected image because it creates a safety mechanism whereby the viewer maintains the ability to detect peripheral cues even in the event of failure by the apparatus. We believe this safety feature is critical to this invention and claim the design of an image-capture and display apparatus such that the projected image leaves an unobstructed margin of the peripheral visual field.